Now, researchers from Beihang University in China and Aalborg University in Denmark have designed a lower-limb robot exoskeleton – a wearable robot – that features natural knee movement to greatly improve patients’ comfort and willingness to wear it for gait rehab.

The robotic exoskeleton is intended to help stroke patients strengthen their physical fitness, aid the rehabilitation training of paralysed patients, or to assist those who need help performing daily activities.

The team focused on the knee joint, one of the most complex mechanical systems within the human body and a critical player during gait.

The knee joint’s motion is actuated by several skeletal muscles along its articular surfaces, and its centre of rotation moves.

Researchers wondered if a parallel mechanism similar to skeletal muscles would be useful for designing a bionic knee joint.

“Our new design features a parallel knee joint to improve the bio-imitability and adaptability of the exoskeleton,” said Weihai Chen, a professor at Beihang University.

The exoskeleton taps a hybrid serial-parallel kinematic structure consisting of a 1-degree of freedom (DOF) hip joint module and a 2-DOF knee joint module in the sagittal plane.